Mark and Howard met in Westchester, CA and started their careers in the band, Crossfire. The band changed their name to, The Turtles, and got a hit with a remake of Dylan's, "It Ain't Me Babe". After several hits and international success, The Turtles folded in 1970. Mark and Howard then joined Frank Zappa and The Mothers of Invention. They did four albums with Frank Zappa and the movie 200 Motels. Zappa was injured by an irate fan in England so Mark and Howard started recording there own music. Due to previous contractual restrictions they were prevented from using their own names, in a musical context, so they became The Phlorescent Leech and Eddie but later shortened it to Flo and Eddie. They released five albums under that name and had a minor hit, Keep It Warm. In between albums and afterwards they worked with many celebrities; Blondie, David Cassidy, Alice Cooper, Duran Duran, Sammy Hagar, John Lennon, The Knack, Ray Manzarek, Keith Moon, The Ramones, T.Rex, Bruce Springsteen, Steely Dan, Stephen Stills, Livingston Taylor and many others. They also did voices for the animated Strawberry Shortcake and Care Bear movies. As of 2013 they were still touring as The Turtles featuring Flo & Eddie.

Mark is currently an Associate Professor at Belmont University and conducts seminars about the music industry for various academic institutions from junior high school to the University level. He also offers consulting on music business through the website Ask Professor Flo.

Howard has co-hosted a syndicated radio show and recorded a reggae album. He wrote the screenplay for My Dinner With Jimi, a film that chronicles the rise of the Turtles, and co-authored the book, Shell Shocked: My Life with the Turtles, Flo and Eddie, and Frank Zappa, etc., which was released in 2013.